Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$208.98	11.406%	$232.8163	$232.82	$232.80	$232.80
Purchase #2	$86.35	4.452%	$90.1943	$90.19	$90.20	$90.20
Purchase #3	$56.38	10.802%	$62.4702	$62.47	$62.45	$62.50
Purchase #4	$233.38	9.756%	$256.1486	$256.15	$256.15	$256.10
Purchase #5	$35.50	11.764%	$39.6762	$39.68	$39.70	$39.70
Purchase #6	$13.55	11.518%	$15.1107	$15.11	$15.10	$15.10
Purchase #7	$52.60	8.650%	$57.1499	$57.15	$57.15	$57.10
7 purchase totals =	$686.74		$753.5662	$753.57	$753.55	$753.50